What I notice on the "tube only" amps, is that most of the tube sound seems to be after the initial transient.I prefer my amp to be transparent, fast and detailed while keeping the holographic soundstage. Not slow and goey "tube sound".
The thicker harmonics and decay.
Also what was surprising was how (because of the traditional tube designs) significant the capacitors played a part in the sound of those other amps.
It was a pain to have to worry about the capacitors as much as the tubes.
As an example, I went thru at least three brands of cathode caps when upgrading the EC Aficionado to get most transparent sound.
And that wasn't even dealing with the larger choice of coupling caps.
In the end I resorted to the stock choice brand, at a higher voltag ratings for upgrading.
So you see other traditional designs rely heavily on designer experience to get all the "ingredients" to play nice together.
Its not as simple as some "Splice" circuit simulation, for most tube circuit designs.
In contrast, see this hybrid design (in these new amps) as forcing all the parts to "behave" in the real world, as in a circuit simulation.